Special adhesive systems are required for the production of laminates and composites, but especially for the production of base materials for flexible printed circuits. Systems such as these have to meet very stringent requirements because, on the one hand, materials that are difficult to bond, such as copper foils for example, have to be bonded to polyimide films and, on the other hand, the composites have to be flexible and also highly heat-resistant. Solvent-containing adhesive systems based on modified polyurethane, polyester, acrylate and epoxy resins are known to the expert for such purposes. In addition to the basic solvent problem, systems of the type in question are often attended by the disadvantage that the cure times are far too long, for example up to 14 days in the case of polyurethane adhesive systems, or the curing temperatures are too high, for example up to 240.degree. C. in the case of epoxy resin or acrylate systems. Water-based systems have been developed with a view to eliminating the solvent problem. Thus, JP 87/153371 and JP 85/118781 describe water-based adhesives for flexible printed circuits which contain dispersions of acrylate (co)polymers and epoxide compounds. A major disadvantage of systems such as these are their relatively long cure times, for example 16 hours at 130.degree. C. in the case of JP 87/153371. JP 87/112676 describes waterborne polyurethane adhesives based on polyurethane dispersions (A) obtained from polytetramethylene glycol (MW 400 to 2000), an organic diisocyanate and a dimethylol carboxylic acid and also hydrazine or dihydrazides as chain-extending agents neutralized with tertiary amines and a water-soluble compound (B) containing 2 or more epoxide or aziridine rings per molecule. Although it is mentioned as an example that various films, for example PET and polypropylene, can be bonded to one another with this adhesive, there is no suggestion that adhesives of the type in question could be suitable for heat-sealable coatings. In addition, there are no references to the production of non-blocking coatings or to the special use for the production of flexible printed circuits.
Accordingly, the problem addressed by the present invention was to provide water-based reactive systems which would be capable of achieving high bond strengths, even in the case of difficult substrates, such as polyimides. In addition, the invention set out to guarantee high flexibility, high insulation resistance, high heat resistance and high solder bath resistance. The cure time would be relatively short and the curing temperature below 200.degree. C. In addition, the particular need for blocking resistance would be satisfied. By blocking resistance is meant the non-tackiness of a film--which has been produced by coating of a substrate with the reactive system according to the invention and subsequent drying--at typical room and storage temperatures. In addition, the invention would provide a new raw material base or a different class of polymers as starting material for such systems.